In transmissions that change the speed of the rotation outputted by a driving source such as an engine, there is one provided with a parking mechanism for holding the stopping state after a vehicle is stopped. For example, Patent Document 1 discloses a parking mechanism that restricts the rotation of an output shaft by engaging a claw portion of a parking pawl with a parking gear secured on an output shaft of a transmission The parking mechanism like this is required to separate the parking pawl from the parking gear for the purpose of turning to an unlocked state in which the rotation of the output shaft is not restricted. For this reason, in the parking mechanism in Patent Document 1, a torsion spring is arranged around the outer periphery of a support shaft rotatably supporting the parking pawl and urges the parking pawl in a releasing direction by its elastic force.
However, in this construction, the position at which the torsion spring urges the parking pawl becomes a position being relatively close to the rotational axis of the parking pawl, so that a strong elastic force is required for the torsion spring. Consequently, a load against the torsion spring in assembling the parking mechanism becomes large, thereby arousing an anxiety that the working property in assembling is degraded. Further, with an increase in elastic force, the torsion spring becomes larger in diameter, and thus, the parking mechanism is liable to become larger in dimension as a whole. To avoid this, for example, Patent Document 2 discloses a parking mechanism supporting a torsion spring by a pin that is arranged to be distanced from the rotational axis of a parking pawl. With this construction, because the position at which the torsion spring urges the parking pawl is distanced from the rotational axis of the parking pawl, it is considered that a torsion spring being relatively weak in elastic force can be used.